Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods excluding the amniotes. All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura, Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems. Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.
Neoteny, also called juvenilization, is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny in modern humans is more significant than in other primates. In progenesis or paedogenesis, sexual development is accelerated.
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata. Urodela is a scientific Latin term based on the Ancient Greek οὐρά δήλη: ourà dēlē "conspicuous tail". Caudata is the Latin for "tailed ones", from cauda: "tail".
The axolotl is a paedomorphic salamander closely related to the tiger salamander. It is unusual among amphibians in that it reaches adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco. These lakes were drained by Spanish settlers after the conquest of the Aztec Empire, leading to the destruction of much of the axolotl's natural habitat.
The tiger salamander is a species of mole salamander and one of the largest terrestrial salamanders in North America.
Ambystomatidae is a family of salamanders belonging to the Suborder Salamandroidea in the class Amphibia. It contains two genera, Ambystoma and Dicamptodon. Ambystoma contains 32 species and are distributed widely across North America, while Dicamptodon contains four species restricted to the Pacific Northwest. These salamanders are mostly terrestrial and eat invertebrates, although some species are known to eat smaller salamanders. They can be found throughout the US and some areas of Canada in damp forests or plains. This family contains some of the largest terrestrial salamanders in the world, the tiger salamander and the coastal giant salamander. Some species are toxic and can secrete poison from their bodies as protection against predators or infraspecific competition. Neoteny has been observed in several species in Ambystomatidae, and some of them like the axolotl live all of their lives under water in their larval stage.
The blue-spotted salamander is a mole salamander native to the Great Lakes states and northeastern United States, and parts of Ontario and Quebec in Canada. Their range is known to extend to James Bay to the north, and southeastern Manitoba to the west.
The ringed salamander is a species of mole salamander native to hardwood and mixed hardwood-pine forested areas in and around the Ozark Plateau and Ouachita Mountains of Arkansas, Oklahoma, and Missouri. This species of salamander has slander body, small head, and long tail. They are usually found to have various dorsal color from dark gray to dark brown. Various close relatives are found such as marbled salamander and spotted salamander. This species of salamander has cannibal behavior especially those in large body size.
The long-toed salamander is a mole salamander in the family Ambystomatidae. This species, typically 4.1–8.9 cm (1.6–3.5 in) long when mature, is characterized by its mottled black, brown, and yellow pigmentation, and its long outer fourth toe on the hind limbs. Analysis of fossil records, genetics, and biogeography suggest A. macrodactylum and A. laterale are descended from a common ancestor that gained access to the western Cordillera with the loss of the mid-continental seaway toward the Paleocene.
The Lake Patzcuaro salamander, locally known as achoque, is a paedomorphic species of salamander found exclusively in Lake Pátzcuaro, a high-altitude lake in the Mexican state of Michoacán. First described in 1870 by Alfredo Dugès, the species is named in honor of the French herpetologist Auguste Duméril. However, the salamander has been used as a food source and an ingredient in traditional medicines by the Purépecha people since the Pre-Columbian era. Ambystoma dumerilii are neotenic, meaning they retain their larval characteristics throughout their entire life. This results in adults that have long, heavily filamented external gills, gill slits lined with tooth-like gill rakers, and caudal fins. When stressed, Ambystoma dumerilii can undergo an incomplete metamorphosis, though this is process significantly decreases their lifespan and is often fatal.
Ambystoma talpoideum, the mole salamander, is a species of salamander found in much of the eastern and central United States, from Florida to Texas, north to Illinois, east to Kentucky, with isolated populations in Virginia and Indiana. Older sources often refer to this species as the tadpole salamander because some individuals remain in a neotenic state. This salamander lives among the leaf litter on the forest floor, migrating to ponds to breed.
The barred tiger salamander or western tiger salamander is a species of mole salamander that lives in lower western Canada, the western United States and northern Mexico.
Ambystoma rivulare is a species of mole salamander in the family Ambystomatidae. Typically gains a lot of population distribution in the Trans-Mexican Volcanic Belt around central Mexico City. Found in various small or medium-sized ponds and lakes that have large and wide range of food options, all within a distance of at least 2 km. It is endemic to Mexico. Its natural habitats are subtropical or tropical moist montane forests and rivers. It is threatened by habitat loss. The larvae, who continue to prey on the same organisms as they grow, prey mainly on ostracods as well as some gastropods and assorted other prey with limited diversity. Ambystoma rivulare continue to live in the river they hatch in post-metamorphosis. Research on the Michoacan Stream Salamander has important implications for the conservation and persistence of these salamanders. The lack of variety in the A. rivulare diet puts them in a precarious situation should environmental factors endanger the ostracod population in their habitat. Further, a study done at the University of Sao Paulo on the diet of A. rivulare shows no relationship between size and the salamander's diet, suggesting a lack of larger prey for the bigger salamanders to eat.
The silvery salamander is a hybrid species of mole salamander from the United States of America and Canada. It is usually between 5.5–7.75 in (14.0–19.7 cm) long and slender, with many small silvery-blue spots on its back and sides. It is brownish grey, and the area around its vent is grey. A unisexual Ambystoma hybrid species, A. platineum has been grouped with other unisexual ambystomatids that take genetic material from Jefferson salamanders, streamside salamanders, small-mouthed salamanders, tiger salamanders and the blue-spotted salamander.
A newt is a salamander in the subfamily Pleurodelinae. The terrestrial juvenile phase is called an eft. Unlike other members of the family Salamandridae, newts are semiaquatic, alternating between aquatic and terrestrial habitats. Not all aquatic salamanders are considered newts, however. More than 100 known species of newts are found in North America, Europe, North Africa and Asia. Newts metamorphose through three distinct developmental life stages: aquatic larva, terrestrial juvenile (eft), and adult. Adult newts have lizard-like bodies and return to the water every year to breed, otherwise living in humid, cover-rich land habitats.
In biology, a klepton and synklepton is a species that requires input from another biological taxon to complete its reproductive cycle. Specific types of kleptons are zygokleptons, which reproduce by zygogenesis; gynokleptons which reproduce by gynogenesis, and tychokleptons, which reproduce by a combination of both systems.
Parthenogenesis is a form of reproduction where eggs develop without fertilization, resulting in unisexual species. This phenomenon is closely related with reproductive modes such as hybridogenesis, where fertilization occurs, but the paternal DNA is not passed on. Among amphibians, it is seen in numerous frog and salamander species, but has not been recorded in caecilians.
Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.
